(a) Field of the Invention
The present invention relates to a secondary battery, and more particularly, to a cooling structure for a secondary battery module having a plurality of unit batteries.
(b) Description of the Related Art
Unlike the primary battery, the secondary battery may be recharged. Lower power secondary batteries comprised of one battery cell are used as the power source for various portable electronic devices such as cellular phones, laptop computers, and camcorders. Bulk size secondary batteries in which a plurality of the battery cells are connected in a pack shape are used as the power source for motor drives, such as those in hybrid electric vehicles.
Depending on the external shape, secondary batteries may be classified into different types, for example, square and cylindrical batteries.
When the secondary batteries are used for motor drives of machines requiring a high power source, such as electric vehicles, the secondary batteries are serially connected to form a battery module.
A battery module is formed by serially connecting a plurality of secondary batteries (hereinafter “unit batteries”).
Each unit battery includes an electrode assembly in which a separator is interposed between a positive electrode and a negative electrode, a container having a space receiving the electrode assembly inside thereof, a cap assembly assembled with the container to seal the container, and a positive terminal and a negative terminal protruded toward the cap assembly and electrically connected to a collector of a positive electrode and a negative electrode of the electrode assembly.
In addition, the unit batteries are spaced apart from each other and the terminals are connected to each other serially or in parallel to form a battery module.
Since the battery module connects several to tens of unit batteries, there is a need to efficiently emit heat generated from each unit battery. In particular, when the secondary battery is used for hybrid electric vehicles, the heat emission is of significant importance.
If the heat emission does not occur properly, a temperature difference between unit batteries results, which lowers charge-discharge efficiency.
In addition, the heat generated from each unit battery may excessively increase the temperature of the secondary battery module, which may cause the unit battery to explode.
In particular, since the battery module for hybrid electric vehicles used for motor drives requires high current charge and discharge, the internal reaction of the secondary battery generates heat, which may lower the performance of the battery.